Pumping gas pedal when starting car w/ fuel injection - CorvetteForum - Chevrolet Corvette Forum Discussion

Go Back   >
Log In 
Register FAQ Search Today's Posts Mark Forums Read Vendor Directory

Off Topic
Off Topic | Non-Corvette

View Poll Results: Pumping; is it bad?
Won't hurt the car 13 43.33%
DON'T DO IT! 17 56.67%
Voters: 30. You may not vote on this poll

Pumping gas pedal when starting car w/ fuel injection

Reply
 
 
 
Thread Tools Search this Thread
Old 05-12-2007, 12:00 AM   #1
Lord Odin
CF Senior Member
Thread Starter
 
Lord Odin's Avatar
 
Member Since: Jul 2001
Location: New Lenox IL
Posts: 3,615
Thanks: 0
Thanked 0 Times in 0 Posts
Default Pumping gas pedal when starting car w/ fuel injection

I have heard that pumping the gas pedal when a car that has fuel injection and is having trouble starting is bad for the car. No explanation as to why but only that it is bad and fuel injection should handle the problem by itself, unlike vehicles with carburetors. What is so bad about pumping the gas?

If the injectors are getting clogged, wouldn't pumping the pedal actually help it in that circumstance?
Lord Odin is offline   Reply With Quote
Old 05-12-2007, 12:08 AM   #2
CGGorman
CF Senior Member
 
CGGorman's Avatar
 
Member Since: Jun 2004
Location: Smile, it's just the internet.
Posts: 20,226
Thanks: 0
Thanked 0 Times in 0 Posts
Default

In some case, the ECU will shut down the injectors if you WOT during cranking. This is a routine inserted to help clear a flooded engine.

Oherwise, I don't know a reason why pumping would help OR hurt.
CGGorman is offline   Reply With Quote
Old 05-12-2007, 12:16 AM   #3
CGGorman
CF Senior Member
 
CGGorman's Avatar
 
Member Since: Jun 2004
Location: Smile, it's just the internet.
Posts: 20,226
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Injectors are basically just electric switches. They either spray or not, depending on te presence of electrical current. The only real variable with a given injector is how long the "switch" is allowed to remain off or on. The throttle in most EFI car until very recently was electromechanical. Mech. in that it opened and closed the throttle blades just like on a carb. Electrical in that there is a sensor mounted on the throttle butterfly shaft that tells the computer how far open the throttle is. The computer uses that info, plus more info from various other sensors (air flow, air temp, crank position+RPM, etc.) to determine how to switch the injectors.

Pumping the throttle is useless in a EFI engine. If it won't start, there is a real problem somewhere.

On a carbureted engine, your foot controls a helluva lot more, such as the choke position and enrichment (squirt of raw fuel for each press of the pedal). The fuel delivery is "dumb". It relies completely upon engine vacuum or your foot (or both) to get fuel out of the fuel bowl.

A cold engine needs a richer mixture to start and run smoothly. On EFI cars, that is handled by the computers. On Carb'd engines, it's the choke. Most people don't have a freakin' clue how to tune a carb to run when the engine is warm, let alone when it's cold or during the transition between the two. Often, that means not enough fuel during cold start, so pumping the throttle will squort a bunch extra in there. It will just lay in the intake for a bit, but it;s enough to get the car running.

Last edited by CGGorman; 05-12-2007 at 12:31 AM.
CGGorman is offline   Reply With Quote
Old 05-12-2007, 12:20 AM   #4
vttedrm
CF Senior Member
 
vttedrm's Avatar
 
Member Since: Jan 2004
Location: Sherwood Park Alberta
Posts: 3,529
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by Lord Odin View Post
I have heard that pumping the gas pedal when a car that has fuel injection and is having trouble starting is bad for the car. No explanation as to why but only that it is bad and fuel injection should handle the problem by itself, unlike vehicles with carburetors. What is so bad about pumping the gas?

If the injectors are getting clogged, wouldn't pumping the pedal actually help it in that circumstance?
My answer is Both. It won't really hurt the car (may flood) but I don't do it.
vttedrm is offline   Reply With Quote
Old 05-12-2007, 12:20 AM   #5
Fastbird
Former Sponsor
 
Fastbird's Avatar
 
Member Since: Mar 2004
Location: Fort Wayne IN
Posts: 7,747
Thanked 50 Times in 43 Posts
Default

Quote:
Originally Posted by CGGorman View Post
In some case, the ECU will shut down the injectors if you WOT during cranking. This is a routine inserted to help clear a flooded engine.

Oherwise, I don't know a reason why pumping would help OR hurt.
Exactly. There's no point to pump the pedal on a fuel injected car UNLESS you know the engine is flooded and you need to clear out the cylinders. Even in that case you simply hold the pedal to the floor until the car starts.
Fastbird is online now   Reply With Quote
Old 05-12-2007, 12:31 AM   #6
gpracer1
CF Senior Member
 
gpracer1's Avatar
 
Member Since: Feb 2006
Location: Phoenix AZ
Posts: 5,202
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by Fastbird93 View Post
Exactly. There's no point to pump the pedal on a fuel injected car UNLESS you know the engine is flooded and you need to clear out the cylinders. Even in that case you simply hold the pedal to the floor until the car starts.
Most injected cars have a "clear flood mode". If you hold the pedal down all the way and then crank the car, the injectors do not squirt fuel.
gpracer1 is offline   Reply With Quote
Old 05-12-2007, 12:32 AM   #7
scorp508
CF Senior Member
 
scorp508's Avatar
 
Member Since: Mar 2000
Posts: 83,055
Thanks: 0
Thanked 0 Times in 0 Posts
Default

C4s put you into a flood clear mode and don't fire the injectors with the pedal at WOT during cranking.
scorp508 is offline   Reply With Quote
Old 05-12-2007, 12:36 AM   #8
comp
CF Senior Member
 
comp's Avatar
 
Member Since: Sep 2003
Location: eville in
Posts: 88,399
Thanks: 0
Thanked 0 Times in 0 Posts
Default

best to try to start 3 times (short cranks) No start smell for fuel,,,turn key on press one time then crank
comp is offline   Reply With Quote
Old 05-12-2007, 01:56 AM   #9
Buffalo Dude
CF Senior Member
St. Jude Donor '07
 
Buffalo Dude's Avatar
 
Member Since: Mar 2001
Location: San Francisco CA
Posts: 11,602
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by CGGorman View Post
Injectors are basically just electric switches. They either spray or not, depending on te presence of electrical current. The only real variable with a given injector is how long the "switch" is allowed to remain off or on. The throttle in most EFI car until very recently was electromechanical. Mech. in that it opened and closed the throttle blades just like on a carb. Electrical in that there is a sensor mounted on the throttle butterfly shaft that tells the computer how far open the throttle is. The computer uses that info, plus more info from various other sensors (air flow, air temp, crank position+RPM, etc.) to determine how to switch the injectors.

Pumping the throttle is useless in a EFI engine. If it won't start, there is a real problem somewhere.

On a carbureted engine, your foot controls a helluva lot more, such as the choke position and enrichment (squirt of raw fuel for each press of the pedal). The fuel delivery is "dumb". It relies completely upon engine vacuum or your foot (or both) to get fuel out of the fuel bowl.

A cold engine needs a richer mixture to start and run smoothly. On EFI cars, that is handled by the computers. On Carb'd engines, it's the choke. Most people don't have a freakin' clue how to tune a carb to run when the engine is warm, let alone when it's cold or during the transition between the two. Often, that means not enough fuel during cold start, so pumping the throttle will squort a bunch extra in there. It will just lay in the intake for a bit, but it;s enough to get the car running.
What he said.
Buffalo Dude is offline   Reply With Quote
Old 05-12-2007, 07:46 AM   #10
Lord Odin
CF Senior Member
Thread Starter
 
Lord Odin's Avatar
 
Member Since: Jul 2001
Location: New Lenox IL
Posts: 3,615
Thanks: 0
Thanked 0 Times in 0 Posts
Default

So there is no possible way of pumping the gas pedal to hurt the car with EFI?
Lord Odin is offline   Reply With Quote
Old 05-12-2007, 07:56 AM   #11
Torqaholic
CF Senior Member
St. Jude Donor '09
 
Torqaholic's Avatar
 
Member Since: May 2006
Location: Mid-Michigan
Posts: 42,891
Thanks: 0
Thanked 3 Times in 2 Posts
Default

If you're wanting to pump the pedal due to problems starting a cold vehicle try turning the key to the on position and waiting a few seconds for the fuel pump to pressurize the system before cranking it over.
Torqaholic is offline   Reply With Quote
Old 05-12-2007, 08:34 AM   #12
Tom/99
CF Senior Member
 
Tom/99's Avatar
 
Member Since: Jun 1999
Location: Houston,Texas USA
Posts: 41,149
Thanked 13 Times in 12 Posts
Default

You don't need to touch the gas pedal when starting a fuel injected car.
Tom/99 is offline   Reply With Quote
Old 05-12-2007, 09:27 AM   #13
Muffin
CF Senior Member
 
Muffin's Avatar
 
Member Since: Jun 1999
Location: Merritt Ils Fl
Posts: 14,925
Thanks: 0
Thanked 0 Times in 0 Posts
Default

What CGGorman said with one small addition:On a MAF car the ECM, through the TPS, reads not only how far the throttle plates are open but also the rate at which the opening is changing. If you pump the gas pedal while the car is starting the ECM can, in a sense,become confused.
Muffin is offline   Reply With Quote
Go Back   CorvetteForum - Chevrolet Corvette Forum Discussion >
Reload this Page
  • Pumping gas pedal when starting car w/ fuel injection
  •  
     
    Reply

    Related Topics
    Thread Thread Starter Forum Replies Last Post
    wont start unless i press gas pedal slider_buck C5 Tech 15 03-22-2016 08:20 AM
    350 motor problem jkann1 C4 Tech/Performance 6 11-01-2015 11:01 PM
    1985 Corvette hard to start HughG C4 Tech/Performance 32 04-20-2014 12:03 PM
    car wont start bad fuel pump ? takovr C4 General Discussion 8 04-20-2013 09:29 AM
    Very interesting discussion about meth injection Bad News C6 Forced Induction/Nitrous 13 03-03-2012 12:43 AM


    Tags
    bad, car, efi, fuel, gas, injected, injection, pedal, press, problems, pump, pumping, start, starting, touch

    Thread Tools Search this Thread
    Search this Thread:

    Click for Advanced Search

    Posting Rules
    You may not post new threads
    You may not post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are Off
    Pingbacks are Off
    Refbacks are Off

    Forum Jump


    All times are GMT -4. The time now is 06:14 AM.